1. Field of the Invention
The present invention relates to devices and methods for running a wear bushing into and retrieving a wear bushing from a well.
2. Description of the Related Art
Wear bushings, or wear sleeves, are used to protect the interior of the wellhead during drilling. A typical wear bushing is landed in the wellhead housing before the bit is run into the well. The wear bushing is then removed after drilling and before the well is lined with casing. Traditionally, separate trips with a running tool and, later, a retrieval tool were required to emplace and them retrieve the wear bushing. An example of this type of system is described in U.S. Pat. No. 5,762,136 issued to Oswald. Unfortunately, the extra trips for the running tool are costly and time consuming.
There are a few systems known that have attempted to couple the operations of running and retrieving the wear bushing with those of running and retrieving the drill bit from the wellbore. Unfortunately, these systems do not, in practice, provide workable solution.
U.S. Pat. No. 3,247,914 issued to Slack describes a technique wherein a wear bushing protector loosely surrounds the drilling string. The diameter of the drill bit is larger than the inside diameter of the protector allowing the protector to be carried top the drill bit for loose placement into and removal from the wellhead housing. However, this sort of arrangement is impractical today since it is preferred to pass a drill bit through the wear bushing during use, and the diameter of drill bits used is smaller than the interior of the wear bushing.
U.S. Pat. No. 3,489,214 issued to Phipps describes a system wherein a wear sleeve also located on a drill collar above the drill bit for placement in a wellhead. The wear sleeve is provided with interior J-slots that can be engaged by pins on the drill collar. If it is desired to retrieve the wear sleeve without bringing the drill bit all the way up and out of the hole, a specialized retriever tool is incorporated into the drill string. The wear sleeve can then be retrieved by lowering the retriever tool down to the level of the wear sleeve and engaging the J-slots of the wear sleeve with pins on the retriever tool. While this type of arrangement is effective, it requires the drill string to be broken down in order to incorporate the retriever tool into the drill string. After the wear sleeve is removed from the well, the drill string must be broken down a second time to remove the wear sleeve and the retriever tool. A further problem with this design is that the downward movement of the drill string is limited by the wear sleeve. The retriever tool cannot pass through the wear sleeve because the outwardly projecting pins and rings prevent passage. If it is desired to advance the drill bit downhole, one must pull the drill string out and break it down to remove the retriever tool.
U.S. Pat. No. 4,625,381 issued to Gravouia, Jr. et al. also describes a system wherein a wear bushing can be retrieved using a retriever section with J-slots. This system suffers from substantially the same drawbacks as the Phipps system
U.S. Pat. No. 4,362,210 issued to Green describes a friction hold wear bushing. A wrench is rotated to cause the specialized wear bushing to selectively engage the casing in a frictional grip.
U.S. Pat. No. 4,995,458 issued to Garbett describes wear bushing retrieval arrangements wherein a latching device is secured to the outside of a length of casing during a late stage of the casing running operation. The latching device engages a groove on the interior of the wear bushing. The wear bushing can then be removed from the wellhead casing by pulling upward on the casing string. It is noted that Garbett""s system involves actually drilling through the wear bushing at the start of drilling.
The prior art arrangements have a number of operational problems. In systems such as those described in Garbett, once the wear bushing has been landed, the drill string cannot be readily moved downwardly further into the wellbore because progress of the retrieval tool becomes blocked by the wear bushing. On the other hand, systems such as those taught in Slack remove the wear bushing every time the bit is removed from the wellbore. This is undesirable. Phipps system requires that the drill string be disassembled to incorporate the retriever tool. Additionally, many prior art techniques do not provide a means for securing the wear bushing to the drill string for running the wear bushing. It would be desirable to have devices and methods that address the problems of the prior art.
Arrangements are described wherein wear bushing can be selectively emplaced in a wellhead housing or removed therefrom. A running tool is used to selectively engage the wear bushing during emplacement and removal. The wear bushing need not be removed each time the drill string is tripped into or out of the well. In addition, the drill string may continue to be lowered after the wear bushing is landed since the running tools described can easily pass through the bushing. Further, the drill string need not be broken down in order to incorporate the running tools.
In a first exemplary embodiment, a running tool is incorporated into the drill string at the outset of drilling operations and provided with a radially expandable C-ring that engages an inner portion of the wear bushing as the drill string is tripped in. Once the wear bushing is landed in the wellhead housing, the C-ring is cammed radially inwardly as the drill string and running tool are disposed further downhole. The drill string and bit may be removed from the well by simply pulling them directly out of the well. If it is desired to remove the wear bushing, such as after a portion of the drilling is completed, this may be accomplished without completely tripping the bit out of the well. The C-ring of the running tool is moved to a radially expanded position by disposing a dart, plug or wiper into the flowbore of the drill string and providing fluid pressure inside the flowbore. The drill string is then moved upwardly to the point that the C-ring engages the wear bushing. Tripping out of the drill string from the well to the point that the running tool is removed will remove the wear bushing as well.
In a second described embodiment, spring-based locking pins that selectively project radially outwardly are used in place of a radially expandable C-ring. The pins initially engage the wear bushing and carry it upon the drill string as the bit is run into the well. After the wear bushing is landed, and the bit disposed lower into the well, the pins are retracted radially and retained in that configuration. As a result, the drill string and bit may be removed from the well without removing the wear bushing. Fluid pressurization within the flowbore of the drill string will cause the pins to expand radially so that the wear bushing may be engaged by the running tool. The wear bushing may then be removed from the well by removing the drill string and running tool from the well.
In a third described embodiment, the drill string is selectively secured to a wear bushing by locking pins that are caused to selectively project radially outwardly from the running tool. The drill string is also secured by a xe2x80x9cweakxe2x80x9d C-ring arrangement to a locking assembly having a set of locking dogs that engage the wellhead. After the wear bushing is seated in the wellhead housing, weight is placed upon the drill string to release the drill string from the locking assembly and the wear bushing.